1. Field of the Invention
The present invention relates to a magnetic head supporting device for supporting magnetic heads in an apparatus for recording and reproducing information on and from a flexible magnetic disk. More particularly, the present invention is concerned with the construction of a gimbal spring incorporated in the magnetic head supporting device of the kind described above.
2. Description of the Prior Art
FIG. 3 shows the construction of a known magnetic head supporting device used in a conventional flexible magnetic disk recording and reproducing apparatus. Gimbal springs 6 and 7 to which magnetic heads 4 and 5 are secured are attached to ends of a stationary base member 1 and a movable base member 2. Pivots 8 and 9 project from the stationary base member 1 and the movable base member 2 so as to be pressed onto the centers of the rear surfaces of the gimbal springs 6 and 7. More specifically, the pivots 8 and 9 support, through the intermediaries of the gimbal springs 6 and 7, the centers of the rear surfaces of the magnetic heads 4 and 5 so as to prevent any positional offset of the magnetic heads 4 and 5. The spring 3 constitutes a fulcrum which enables the movable base member 3 to swing up and down. A reference numeral 10 denotes a pressurizing spring acting between a spring retainer 11 fixed to the stationary base member 1 and the movable base member 2 so as to resiliently press the movable base member 2 towards the stationary base member 1, whereby the magnetic heads 4 and 5 are pressed onto both sides of a flexible magnetic disk 12.
FIG. 4 is a plan view illustrating the positional relationship between the gimbal spring, magnetic head and the pivot on the movable base member. It should be noted, however, that the illustrated positional relationship may be applied also to the members associated with the stationary base member. The magnetic head 5 is disposed on the center of the gimbal spring 7, while the pivot 9 presses the center G of the rear surface of the magnetic head 5 through the gimbal spring 7. The gimbal spring 7 is formed from a thin sheet of a resilient material by punching or etching. As will be seen from FIG. 4, the gimbal spring has a central rectangular portion a connected to an intermediate rectangular frame portion through narrow bridge portions c and an outer holder portion d which is connected to the intermediate frame portion b through narrow bridge portions e which are perpendicular to the bridge portions c. With this arrangement, the central rectangular portion a can slightly pitch and roll with respect to the outer holding portion d. In FIG. 4, an arrow A indicates the direction in which the magnetic disk runs. Thus, the central rectangular portion a can pitch in the direction of running of the rotary disk, i.e., about an axis X--X, and roll also in the radial direction of the disk, i.e., about an axis Y--Y. Specifically, in the arrangement shown in FIG. 4, the central rectangular portion a has a degree of freedom of rotation in the circumferential direction of the disk with respect to the intermediate rectangular frame b which in turn has a degree of freedom of rotation in the radial direction of the disk with respect to the outer holding portion d. This arrangement, however, may be reversed such that the central rectangular portion a has a degree of freedom of rotation in the radial direction of the disk with respect to the intermediate rectangular frame b which in turn has a degree of freedom of rotation in the circumferential direction of the disk with respect to the outer holding portion d, as shown in FIG. 5.
When the magnetic disk runs in the direction of an arrow A in FIG. 6, a force shown by an arrow F is produced along the surface of the magnetic disk due to friction between the surface of the magnetic head 5 and the surface of the magnetic disk, causing the magnetic head 5 to be inclined in the direction of running of the surface of the magnetic disk, as shown in FIG. 6 in a somewhat exaggerated manner for an easier understanding. This inclination causes the magnetic head 5 to contact with the magnetic disk 12 at the upstream end, i.e., at the left end as viewed in FIG. 6. In consequence, the state of contact between the magnetic head and the magnetic disk is rendered unstable, resulting in various problems such as deterioration in the electromagnetic conversion characteristics and damages in the magnetic disk.